SearcharxivSearch

arXiv · astro-ph/9910234

Summary: Comments on the State of our Subject

Abstract

This conference shows the impressive rate of advances in the observations and theoretical interpretations of large-scale structure. But to explain my feeling that we may still have a lot to learn I offer some comments on our sociology, informed by social construction, in adopting lines of thought that tend not to follow straightforward readings of what is observed. Thus galaxies are thought to be affected by environment, not only in the morphology-density relation, but also as the cause of biased formation. But the Tully-Fisher and fundamental plane relations do not allow much room for the contingencies of environment. It is thought that the galaxy distribution is not likely to be closely related to the mass, yet most dynamical analyses indicate that if the mean density is low then optically selected galaxies are good mass tracers. The evidence is that at redshift unity the larger spiral and elliptical galaxies were by and large in place, as were a good fraction of the great clusters of galaxies. These galaxies evolve slowly at $z<1$, yet we hears of rapid evolution not much before this, in galaxy formation. Perhaps all these examples are misleading. But, as Kuhn has taught us, complex interpretations of simple phenomena have been known to be precursors of paradigm shifts.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

P. J. E. Peebles. 1999-10-13. Summary: Comments on the State of our Subject. https://arxiv.org/abs/astro-ph/9910234

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

A Cyclical Baryonic Big Bang Explains the Universe

Our universe has multiple examples of unexplained gravitational losses in black holes and neutron stars. The smallest black holes of about 4 solar masses means the maximum baryon density ρ\approx 10^{17} grams/cm^3. Any collapse of the universe will stop with a scale factor \approx 10^{13} cm. and radiation energy \approx 10 GeV. Due to higher squeezed core baryons, the outer part of the mass transferred energy to the core and became dark matter. After contraction reduced particle motion and gravitation, the core radiation energy propelled pieces of the shell into the universe. Each of these masses captured hot core gases according to its gravitational size, forming proto-galaxies. A cold shell and a hot core explain the Planck spectrum and large galaxy formation in the early universe. Thus the universe was never radiation dominant.The universe will remain cyclical as any increase in entropy of matter will be crushed back to neutrons during the contraction phase.

astro-ph

A survey of debris trails from short-period comets

We observed 34 comets using the 24 micron camera on the Spitzer Space Telescope. Each image contains the nucleus and covers at least 10^6 km of each comet's orbit. Debris trails due to mm-sized or larger particles were found along the orbits of 27 comets; 4 comets had small-particle dust tails and a viewing geometry that made debris trails impossible to distinguish; and only 3 had no debris trail despite favorable observing conditions. There are now 30 Jupiter-family comets with known debris trails, of which 22 are reported in this paper for the first time. The detection rate is >80%, indicating that debris trails are a generic feature of short-period comets. By comparison to orbital calculations for particles of a range of sizes ejected over 2 yr prior to observation, we find that particles comprising 4 debris trails are typically mm-sized while the remainder of the debris trails require particles larger than this. The lower-limit masses of the debris trails are typically 10^11 g, and the median mass loss rate is 2 kg/s. The mass-loss rate in trail particles is comparable to that inferred from OH production rates and larger than that inferred from visible-light scattering in comae.

astro-ph

Deformation procedure for scalar fields in cosmology

This work offers an extension of the deformation procedure introduced in field theory to the case of standard cosmology in the presence of real scalar field in flat space-time. The procedure is shown to work for many models, which give rise to several different cosmic scenarios, evolving under the presence of first-order differential equations which solve the corresponding equations of motion very appropriately.

astro-ph